This invention relates in general to vehicle disc brake assemblies and in particular to an improved structure for a rotor adapted for use in such a vehicle disc brake assembly.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefor, are well known in the art.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. A caliper assembly is slidably supported by pins secured to an anchor plate. The anchor plate is secured to a non-rotatable component of the vehicle, such as the vehicle frame. The caliper assembly includes a pair of brake shoes which are disposed on opposite sides of the rotor. The brake shoes are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from opposed axial sides or braking surfaces of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed braking surfaces of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the opposed braking surfaces of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.
A considerable amount of heat is generated between the rotor and the brake shoes during braking. In order for a rotor to be able to adequately absorb the heat generated during a given stop, as well as to sufficiently cool to a safe operating temperature for the next stop, it is known to form the rotor having a "vented" or "ventilated" design. A conventional ventilated rotor includes a pair of spaced apart brake friction plates which are connected together by a plurality of ribs or posts. U.S. Pat. No. 5,188,203 to Winter, U.S. Pat. No. 4,928,798 to Watson et al., U.S. Pat. No. 4,865,167 to Giorgetti et al., German No. 4,210,449, German Patent No. 4,210,448, German Patent No. 3,527,577, and European Patent No. 77,433 disclose prior art ventilated brake rotors.
In a ventilated rotor, the particular shapes and spacings of the ribs or posts is important for several reasons. First, the shapes and spacings of the ribs or posts should not restrict the flow of cooling air through interior passageways defined therebetween. At the same time, the shapes and spacings of the ribs or posts should provide the rotor with sufficient strength or rigidity. This is especially important at the outer radial portion of the rotor, inasmuch as the brake pads generally apply a greater braking pressure in this region. Additionally, the shape and spacing of the ribs or posts should not add unnecessary rotating mass and unsprung weight to the vehicle, which adversely affects the performance, handling, and fuel economy of the vehicle. Thus, it would be desirable to provide an improved structure for a ventilated rotor adapted for use in a disc brake assembly which provides satisfactory heat capacity and rigidity.